1. Field of the Invention
The present invention relates to a flight control indicator for aircraft.
Such an indicator is more specifically adapted to a rotary-wing aircraft, especially a helicopter.
2. Background Art
The flight of a helicopter is controlled by monitoring numerous instruments on the flight panel, which instruments are for the most part representative of the operation of the engine assembly and of the aircraft. For physical reasons there are numerous limitations which the pilot must take into account at each moment of the flight. These various limitations generally depend on the flight phase and on the outside conditions.
Most helicopters constructed at present are equipped with one or two turboengines, generally of the free turbine type. The power is then tapped off from a low-pressure stage of the turbine, which stage is mechanically independent of both the compressor and the high-pressure stage of the turbine. The power turbine of a turboengine rotating at between 20,000 and 50,000 revolutions a minute, a special reduction box is necessary for the link to the rotor(s): the main gearbox (BTP).
The thermal limitations of the engine and the torque limitations of the main gearbox make it possible to define three normal regimes of engine use:
the takeoff regime, which can be used for five to ten minutes, corresponding to a gearbox torque level and engine turbine heatup which are acceptable for a limited time without appreciable degradation: this is the maximum power at takeoff (PMD), PA1 the maximum continuous regime during which, at no time are either the capabilities of the gearbox or those resulting from the maximum acceptable continuous heatup in front of the high-pressure blading of the first stage of the turbine exceeded: this is the maximum continuous power (PMC), PA1 the maximum transient regime, possibly buttressed by regulation: we then speak of maximum transient power (PMT). PA1 the emergency regime during which the capabilities of the gearbox on the input stages and the thermal capabilities of the engine are used to the maximum: we speak of superemergency power (PSU) which can be used for 30 seconds running, at most, and three times during a flight. Use of the PSU entails the dismantling and overhauling of the engine; PA1 the emergency regime during which the capabilities of the gearbox on the input stages and the capabilities of the engine are largely used: we then speak of maximum emergency power (PMU) which can be used for two minutes after the PSU or two minutes thirty seconds running, at most; PA1 the emergency regime during which the capabilities of the gearbox on the input stages and the thermal capabilities of the engine are used without damage: we speak of intermediate emergency power (PIU) which can be used for thirty minutes or continuously for the remainder of the flight following the engine fault. PA1 sensors able to deliver information relating to various parameters for monitoring the engines, namely the gas generator regime (Ng), the free turbine inlet gas ejection temperature (T4), the engine torque (Cm), PA1 means for processing the information arising from said sensors, and PA1 display means which present, on a display screen, the processed information relating to the parameter, from among said monitoring parameters, whose current value is closest to the limit value for said parameter, is noteworthy, according to the invention, in that said display means present a single dial furnished with two needles, each of them corresponding to a respective engine, and positioned in such a way that, when the engines are operating normally, the two needles are merged.
There are also emergency overpower regimes on multi-engine machines, used in the event of a faulty engine:
The engine manufacturer establishes, through calculations or tests, the curves of available power of a turboengine as a function of altitude and temperature, and does so for each of the regimes defined above.
The limitations indicated are generally monitored via three parameters: the gas generator regime (Ng), the engine torque (Cm) and the free turbine inlet gas ejection temperature (T4).
French patent application FR-96 07040 discloses a flight control indicator which identifies, among the essential engine monitoring parameters, the one which is closest to its limit. The information relating to the limitations to be complied with are thus grouped together on a single display, thereby making it possible, on the one hand, to produce a summary and present only the result of this summary so as to simplify the pilot's task and, on the other hand, to save space on the instrument panel. A "limiting parameter" is thus obtained from among said engine monitoring parameters, the current value of which is closest to the limit value for said parameter. For this reason, such an indicator will hereinafter also be designated by the expression "first limitation instrument", or "IPL" for short.